(06-17) 14:40 PDT SANTA CRUZ -- A 16-year-old boy was arrested early Tuesday on suspicion of involuntary manslaughter after he killed a 15-year-old friend in Santa Cruz in what appears to be an unintentional shooting with a stolen gun, police said.

Detectives had worked through the night trying to piece together what led to the shooting inside an apartment complex at 238 Center St., said Deputy Police Chief Steve Clark.

At 6:45 p.m. Monday, police reported finding the teen victim, who was visiting from Watsonville, still alive in a bedroom with a gunshot wound to his upper chest and neck. Responding officers did CPR but the teen died at the scene, Clark said.

Eight other people who were inside the apartment during the shooting were questioned, Clark said. Detectives determined the suspect, who is from Santa Cruz and lives at the apartment, likely unintentionally shot the victim, who was his friend.

The suspect, whom police did not name, was booked into Santa Cruz County's juvenile hall on suspicion of involuntary manslaughter.

"The charge reflects that it may have been unintentional but it was not accidental," Clark said. "There were some intentional behaviors that had to happen leading up to this. We know the gun had to be displayed in some way."

Officers found the handgun believed to have been used in the shooting outside the apartment. The gun was reported stolen in May from a vehicle in east Santa Cruz, police said.

Clark said the suspect is a gang member, but that his affiliation was not thought to be a motive in the shooting.